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Not accounting for competing events in survival analysis can lead to biased estimates, as individuals who die from other causes do not have the opportunity to develop the event of interest. Formal definitions and considerations for causal effects in the presence of competing risks have been published, but not for the mediation analysis setting. We propose, for the first time, an approach based on the path-specific effects framework to account for competing risks in longitudinal mediation analysis with time-to-event outcomes. We do so by considering the pathway through the competing event as another mediator, which is nested within our longitudinal mediator of interest. We provide a theoretical formulation and related definitions of the effects of interest based on the mediational g-formula, as well as a detailed description of the algorithm. We also present an application of our algorithm to data from the Strong Heart Study, a prospective cohort of American Indian adults. In this application, we evaluated the mediating role of the blood pressure trajectory (measured during three visits) on the association between arsenic and cadmium, in separate models, with time to cardiovascular disease, accounting for competing risks by death. Identifying the effects through different paths enables us to evaluate the impact of metals on the outcome of interest, as well as through competing risks, more transparently.

In this letter, we demonstrate for the first time the creation of Josephson-like superconducting nanojunctions using a thermal scanning probe to directly inscribe weak links into microstrips of YBa2Cu3O7-x (YBCO). Our method effectively reduces the critical current (Ic) over an order of magnitude. The resulting nanobridges exhibit clear evidence of Josephson effects, of SNS-type junctions, as shown by both the DC and AC Josephson effects. This approach provides a novel and flexible method for scaling up quantum mechanical circuits that operate at liquid nitrogen temperatures. Additionally, it offers a promising pathway for modifying properties of the junctions in-situ and post fabrication., Comment: 14 pages, 4 figures

In the rapidly evolving field of multimedia services, video streaming has become increasingly prevalent, demanding innovative solutions to enhance user experience and system efficiency. This paper introduces a novel approach that integrates user digital twins-a dynamic digital representation of a user's preferences and behaviors-with traditional video streaming systems. We explore the potential of this integration to dynamically adjust video preferences and optimize transcoding processes according to real-time data. The methodology leverages advanced machine learning algorithms to continuously update the user's digital twin, which in turn informs the transcoding service to adapt video parameters for optimal quality and minimal buffering. Experimental results show that our approach not only improves the personalization of content delivery but also significantly enhances the overall efficiency of video streaming services by reducing bandwidth usage and improving video playback quality. The implications of such advancements suggest a shift towards more adaptive, user-centric multimedia services, potentially transforming how video content is consumed and delivered.

The development of a materials platform that exhibits both superconducting and semiconducting properties is an important endeavour for a range of emerging quantum technologies. We investigate the formation of superconductivity in nanowires fabricated with silicon-on-insulator (SOI). Aluminium from deposited contact electrodes is found to interdiffuses with the Si nanowire structures to form an Al-Si alloy along the entire length of the predefined nanowire device over micron length scales at temperatures well below that of the Al-Si eutectic. The resultant transformed nanowire structures are layered in geometry with a continuous Al-Si alloy wire sitting on the buried oxide of the SOI and a residual Si cap sitting on top of the wire. The phase transformed material is conformal with any predefined device patterns and the resultant structures are exceptionally smooth-walled compared to similar nanowire devices formed by silicidation processes. The superconducting properties of a mesoscopic AlSi ring formed on a SOI platform are investigated. Low temperature magnetoresistance oscillations, quantized in units of the fluxoid, h/2e, are observed., Comment: 11 pages, 9 figures

The beginning of the modern education and the introduction of the foreign languages in Ethiopia are the two faces of a single coin. And this paper mainly shows how and when foreign languages are introduced into Ethiopia following the footsteps of the introduction and expansion of modern education. It is done using secondary sources. It also gives brief explanations on the statuses and the roles of those foreign languages during different times starting from their introduction up to present. The absence of well-documented literature on this topic motivates the author to work on it. It is true that this topic is shallowly discussed whenever researchers have been reviewing the introduction and expansion of modern education into Ethiopia. The topic has been investigated as a minor agenda whenever researchers have been reviewing the education policies of Ethiopia as their major task. However, this research has reversed the common trend by giving due attention to the foreign languages. Hence, this paper could be used as a useful source document for any interested researchers who really want to study on it since no or less organized literature is available. On this review, English language is given more focus since it is the dominant language comparing to the other foreign languages which have been introduced to Ethiopia.

Use of healthcare services is inadequate in Ethiopia in spite of the high burden of diseases. User-fee charges are the most important factor for this deficiency in healthcare utilization. Hence, the country is introducing community based and social health insurances since 2010 to tackle such problems. This study was conducted cross-sectionally, in March 2013, to assess willingness of rural households to pay for community-based health insurance in Debub Bench district of Southwest Ethiopia. Two-stage sampling technique was used to select 845 households. Selected households were contacted using simple random sampling technique. Double bounded dichotomous choice method was used to illicit the willingness to pay. Data were analyzed with STATA 11. Krinsky and Rob method was used to calculate the mean/median with 95% CI willingness to pay after the predictors have been estimated using Seemingly Unrelated Bivariate Probit Regression. Eight hundred and eight (95.6%) of the sampled households were interviewed. Among them 629(77.8%) households were willing to join the proposed CBHI scheme. About 54% of the households in the district were willing to pay either the initial or second bids presented. On average, these households were willingness to pay was 162.61 Birr per household (8.9 US$) annually. If the community based health insurance is rolled out in the district, about half of households will contribute 163 Birr (8.9 US$) annually. If the premium exceeds the amount specified, majority of the households would not join the scheme. Key words: community based health insurance, willingness to pay, contingent valuation method, double bounded dichotomous choice, Krinsky and Robb, rural households, Ethiopia.

The metallicity and its relationship with other galactic properties is a fundamental probe of the evolution of galaxies. In this work, we select about 750,000 star-forming spatial pixels from 1122 blue galaxies in the MaNGA survey to investigate the global stellar mass - local stellar mass surface density - gas-phase metallicity ($M_*$ - $\Sigma_*$ - $Z$ ) relation. At a fixed $M_*$, the metallicity increases steeply with increasing $\Sigma_*$. Similarly, at a fixed $\Sigma_*$, the metallicity increases strongly with increasing $M_*$ at low mass end, while this trend becomes less obvious at high mass end. We find the metallicity to be more strongly correlated to $\Sigma_*$ than to $M_*$. Furthermore, we construct a tight (0.07 dex scatter) $M_*$ - $\Sigma_*$ - $Z$ relation, which reduces the scatter in the $\Sigma_*$ - $Z$ relation by about 30$\%$ for galaxies with $7.8 < {\rm log}(M_*/M_\odot) < 11.0$, while the reduction of scatter is much weaker for high-mass galaxies. This result suggests that, especially for low-mass galaxies, the $M_*$ - $\Sigma_*$ - $Z$ relation is largely more fundamental than the $M_*$ - $Z$ and $\Sigma_*$ - $Z$ relations, meaning that both $M_*$ and $\Sigma_*$ play important roles in shaping the local metallicity. We also find that the local metallicity is probably independent on the local star formation rate surface density at a fixed $M_*$ and $\Sigma_*$. Our results are consistent with the scenario that the local metallicities in galaxies are shaped by the combination of the local stars formed in the history and the metal loss caused by galactic winds., Comment: 14 pages, 8 figures; accepted by ApJ

We investigate the spatially-resolved star formation main sequence in star-forming galaxies (SFGs) using Integral Field Spectroscopic (IFS) observations from the Mapping Nearby Galaxies at the Apache Point Observatory (MaNGA) survey. We demonstrate that the correlation between the stellar mass surface density ($\Sigma_*$) and star formation rate surface density ($\Sigma_{\mathrm{SFR}}$) holds down to sub-galactic scale, leading to the Sub-Galactic Main Sequence (SGMS). By dividing galaxies into two populations based on their recent mass assembly modes, we find the resolved main sequence in galaxies with 'outside-in' mode is steeper than that in galaxies with 'inside-out' mode. This is also confirmed on a galaxy-by-galaxy level, where we find the distributions of SGMS slopes for individual galaxies are clearly separated for the two populations. When normalizing and stacking the SGMS of individual galaxies on one panel for the two populations, we find the inner regions of galaxies with 'inside-out' mode statistically exhibit a suppression in star formation, with a less significant trend in the outer regions of galaxies with 'outside-in' mode. In contrast, the inner regions of galaxies with 'outside-in' mode and the outer regions of galaxies with 'inside-out' mode follow a slightly sub-linear scaling relation with a slope $\sim$0.9, which is in good agreement with previous findings, suggesting that they are experiencing a universal regulation without influences of additional physical processes., Comment: 11 pages, 9 figures, accepted for publication in ApJ

In this work, we present a detailed photophysical analysis of recently-discovered optically stable, single photon emitters (SPEs) in Gallium Nitride (GaN). Temperature-resolved photoluminescence measurements reveal that the emission lines at 4 K are three orders of magnitude broader than the transform-limited widths expected from excited state lifetime measurements. The broadening is ascribed to ultra-fast spectral diffusion. Continuing the photophysics study on several emitters at room temperature (RT), a maximum average brightness of ~427 kCounts/s is measured. Furthermore, by determining the decay rates of emitters undergoing three-level optical transitions, radiative and non-radiative lifetimes are calculated at RT. Finally, polarization measurements from 14 emitters are used to determine visibility as well as dipole orientation of defect systems within the GaN crystal. Our results underpin some of the fundamental properties of SPE in GaN both at cryogenic and RT, and define the benchmark for future work in GaN-based single-photon technologies.

On demand single photon emitters (SPEs) play a key role across a broad range of quantum technologies, including quantum computation, quantum simulation, quantum metrology and quantum communications. In quantum networks and quantum key distribution protocols, where photons are employed as flying qubits, telecom wavelength operation is preferred due to the reduced fibre loss. However, despite the tremendous efforts to develop various triggered SPE platforms, a robust source of triggered SPEs operating at room temperature and the telecom wavelength is still missing. Here we report a triggered, optically stable, room temperature solid state SPE operating at telecom wavelengths. The emitters exhibit high photon purity (~ 5% multiphoton events) and a record-high brightness of ~ 1.5 MHz. The emission is attributed to localized defects in a gallium nitride (GaN) crystal. The high performance SPEs embedded in a technologically mature semiconductor are promising for on-chip quantum simulators and practical quantum communication technologies., Comment: Comments welcome

Solid state single photon emitters (SPEs) are one of the prime components of many quantum nanophotonics devices. In this work, we report on an unusual, photo-induced blinking phenomenon of SPEs in gallium nitride (GaN). This is shown to be due to the modification in the transition kinetics of the emitter, via the introduction of additional laser-activated states. We investigate and characterize the blinking effect on the brightness of the source and the statistics of the emitted photons. Combining second-order correlation and fluorescence trajectory measurements, we determine the photo-dynamics of the trap states and characterize power dependent decay rates and characteristic off-time blinking. Our work sheds new light into understanding solid-state quantum system dynamics and, specifically, power-induced blinking phenomena in SPEs., Comment: Final version appeared in Phys. Rev. B 96, 041203(R) (2017)

Single photon emitters play a central role in many photonic quantum technologies. A promising class of single photon emitters consists of atomic color centers in wide-bandgap crystals, such as diamond silicon carbide and hexagonal boron nitride. However, it is currently not possible to grow these materials as sub-micron thick films on low-refractive index substrates, which is necessary for mature photonic integrated circuit technologies. Hence, there is great interest in identifying quantum emitters in technologically mature semiconductors that are compatible with suitable heteroepitaxies. Here, we demonstrate robust single photon emitters based on defects in gallium nitride (GaN), the most established and well understood semiconductor that can emit light over the entire visible spectrum. We show that the emitters have excellent photophysical properties including a brightness in excess of 500x10^3 counts/s. We further show that the emitters can be found in a variety of GaN wafers, thus offering reliable and scalable platform for further technological development. We propose a theoretical model to explain the origin of these emitters based on cubic inclusions in hexagonal gallium nitride. Our results constitute a feasible path to scalable, integrated on-chip quantum technologies based on GaN.

Bulk hexagonal boron nitride (hBN) is a highly nonlinear natural hyperbolic material that attracts major attention in modern nanophotonics applications. However, studies of its optical properties in the visible part of the spectrum and quantum emitters hosted by bulk hBN have not been reported to date. In this work we study the emission properties of hBN crystals in the red spectral range using sub-bandgap optical excitation. Quantum emission from defects is observed at room temperature and characterized in detail. Our results advance the use of hBN in quantum nanophotonics technologies and enhance our fundamental understanding of its optical properties., Comment: In press in Physical Review Applied

Electrically driven emission from negatively charged silicon-vacancy, (SiV)- centres in single crystal diamond is demonstrated. The SiV centres were generated using ion implantation into an intrinsic (i) region of a p-i-n single crystal diamond diode. Both electroluminescence and the photoluminescence signals exhibit the typical emission that is attributed to the (SiV)- centres. Under forward and reversed biased PL measurements, no signal from the neutral (SiV)0 defect could be observed. The realization of electrically driven (SiV)- emission is promising for scalable nanophotonics devices employing colour centres in single crystal diamond.

Single photon sources are required for a wide range of applications in quantum information science, quantum cryptography and quantum communications. However, so far majority of room temperature emitters are only excited optically, which limits their proper integration into scalable devices. In this work, we overcome this limitation and present room temperature electrically triggered light emission from localized defects in zinc oxide (ZnO) nanoparticles and thin films. The devices emit at the red spectral range and show excellent rectifying behavior. The emission is stable over an extensive period of time, providing an important prerequisite for practical devices. Our results open up possibilities to build new ZnO based quantum integrated devices that incorporate solid-state single photon sources for quantum information technologies.

This paper develops a framework for fitting functions with domains in the Euclidean space, when data are sparse but a slow variation allows for a useful fit. We measure the variation by Lipschitz Bound (LB). Functions which admit smaller LB are considered to vary more slowly. Since most functions in practice are wiggly and do not admit a small LB, we extend this framework by approximating a wiggly function, f, by ones which admit a smaller LB and do not deviate from f by more than a specified Bound Deviation (BD). In fact for any positive LB, one can find such a BD, thus defining a trade-off function (LB-BD function) between the variation measure (LB) and the deviation measure (BD). We show that the LB-BD function satisfies nice properties: it is non-increasing and convex. We also present a method to obtain it using convex optimization. For a function with given LB and BD, we find the optimal fit and present deterministic bounds for the prediction error of various methods. Given the LB-BD function, we discuss picking an appropriate LB-BD pair for fitting and calculating the prediction errors. The developed methods can naturally accommodate an extra assumption of periodicity to obtain better prediction errors. Finally we present the application of this framework to air pollution data with sparse observations over time.

During the spring semester 2003, faculty members in the Colleges of Education and Arts & Sciences were asked to submit their fall 2002 semester syllabi that reflect the integration of technology into the courses they teach as a result of attending 12-15 weeks faculty development/training workshops. Furthermore, a survey was designed to extract information as to what extent faculty use technology into their courses and to what extent they require their students to use technology in the classroom. During the 2001-02 academic year, 32 faculty members from the Colleges Education and Arts and Sciences participated the PT3 faculty development implementation grant workshops. The purpose of this study is to share experiences related to this faculty development effort during the first year.

The absolute photodetachment cross section of OH- anions at a rotational and translational temperature of 170K is determined by measuring the detachment-induced decay rate of the anions in a multipole radio-frequency ion trap. In comparison with previous results, the obtained cross section shows the importance of the initial rotational state distribution. Using a tomography scan of the photodetachment laser through the trapped ion cloud, the derived cross section is model-independent and thus features a small systematic uncertainty. The tomography also yields the column density of the OH- anions in the 22-pole ion trap in good agreement with the expected trapping potential of a large field free region bound by steep potential walls., Comment: Phys. Rev. Lett., in press

This study investigated curriculum media centers (CMCs), i.e., centers that provide print and non-print materials, equipment, and support services to faculty and students in teacher education programs. Questionnaires were sent to CMC coordinators/directors and college executives at 103 selected institutions that prepare elementary, middle, and secondary school teacher candidates in 19 states representing the membership of the North Central Association (Arizona, Arkansas, Colorado, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, New Mexico, North Dakota, Ohio, Oklahoma, South Dakota, West Virginia, Wisconsin, and Wyoming). The findings of this study are based on an 81% rate of response from the CMC college executives and 79% from coordinators. Objectives of the survey were to: (1) provide information to administrators for planning and managing CMCs; (2) obtain data on CMC staff, services, facilities, and collections; (3) determine strategies for developing instructional media support via the CMC in the implementation of teacher education programs; (4) examine the effect of National Council for Accreditation of Teacher Education (NCATE) standards on CMCs; and (5) develop a media management model to improve planning and integration of CMCs in teacher education programs. Data reported include a descriptive profile of CMCs, information on preservice and inservice teacher education classes scheduled in the CMC, and perceptions of barriers to change in CMCs. Implications for CMC planning are presented. (7 references) (MES)

Purpose: This article contributes new empirical evidence and nuanced analysis on the gender difference in access to extension services and how this translates to observed differences in technology adoption and agricultural productivity. Approach: It looks at the case of Ethiopia, where substantial investments in the extension system have been made, but the coverage and effect of these investments on female and male producers are not well-understood. This article employs a cross-sectional instrumental-variable regression method using a regionally representative data set of more than 7500 households in four major regions in Ethiopia during the 2010 main season. Findings: Female heads of households and plot-managers are less likely to get extension services through various channels and less likely to access quality services than their male counterparts after controlling for other factors. Receiving advice from extension agents is positively related to adoption of improved seed and fertiliser for both female and male, as hypothesised. However, beyond their influence through fertiliser and improved seed use, visits by or advice from agents are not significant or negatively significant in all productivity models estimated for females and males, which is in contrast to past studies. In some crop-productivity models estimated, it is the perceived quality of agents' visits and access to radio that appear to be positively significant factors in explaining productivity levels for both females and males. Practical implications: Results highlight the need for stratified productivity models by gender and crop in future research. In terms of policy implication, results highlight the need to focus on quality of service and alternative channels of information, such as radio, to improve productivity. Originality/value: This article utilises a large-sample data set; uses the instrumental-variable regression method to address selection bias and endogeneity issues in productivity models; and stratifies the analyses to account for differentiated production functions by gender and crop.

A patented microsystem Stirling cooler is under development with potential application to electronics, sensors, optical and radio frequency (RF) systems, microarrays, and other microsystems. The microsystem Stirling cooler is most suited to volume-limited applications that require cooling below the ambient or sink temperature. Primary components of the planar device include: two diaphragm actuators that replace the pistons found in traditional-scale Stirling machines; and a micro-regenerator that stores and releases thermal energy to the working gas during the Stirling cycle. The use of diaphragms eliminates frictional losses and bypass leakage concerns associated with pistons, while permitting reversal of the hot and cold sides of the device during operation to allow precise temperature control. Three candidate microregenerators were custom fabricated for initial evaluation: two constructed of porous ceramic, and one made of multiple layers of nickel and photoresist in an offset grating pattern. An additional regenerator was prepared with a random stainless steel fiber matrix commonly used in existing Stirling machines for comparison to the custom fabricated regenerators. The candidate regenerators were tested in a piezoelectric-actuated test apparatus designed to simulate the Stirling refrigeration cycle. In parallel with the regenerator testing, electrostatically-driven comb-drive diaphragm actuators for the prototype device have been designed for deep reactive ion etching (DRIE) fabrication.